1. Field of the Invention
The present invention relates to an air conditioning system comprising a blower and a heat exchanger effectively used in an automotive.
2. Description of the Related Art
In recent years, what is called a "semicentral unit" has often been employed for reducing the size of an automotive air conditioning system. A semicentral unit comprises a blower arranged in front of the front passsenger seat, and heat exchangers such as an evaporator and a heat core are arranged longitudinally in the center console of an automotive vehicle (FIG. 1). As a result, the air sent under pressure from the blower turns about 90.degree. at a point upstream of the evaporator and flows into the evaporator.
The semicentral unit can be reduced in size as compared with what is called the transverse unit comprising a blower, an evaporator and a heat core arranged along the transverse direction of the vehicle. Also, as compared with the transverse unit, the air path from the blower to the air outlet in the cabin is shortened, and therefore the pressure loss in the air path can be reduced.
In the semicentral unit having a shorter air path than the transverse unit, however, the noise generated in the blower propagates to the interior of the cabin from the air outlet in the cabin without being sufficiently attenuated in the air-conditioning system (air-conditioning casing), thereby leading to the problem of a larger noise than the transverse unit.
Experiments and study conducted by the inventors have confirmed that a noise of about 1 kHz to 2 kHz in frequency is generated most conspicuously in what is called the face blowout mode in which the length of the air path is shortest.